It’s not uncommon for homeowners to hear noises coming from their heating systems at one time or another throughout the winter, especially in older homes. However, it’s important to note the type of noise and how loud it is.

Anything beyond the regular sounds that mean your heater is on and working should be checked out immediately. Unusual or loud noises may indicate a problem with your system.

Types of Furnace Noises

The following are all types of furnace noises that indicate something might be wrong. As you read through the list, we’ll discuss what the problem might be and whether there are any DIY solutions you can try before calling a professional HVAC technician.

Loud Boom

Sometimes your furnace will make a loud “boom” sound when you first turn the heat on for the season. This is usually due to dirty burners causing a delayed ignition and is something your HVAC technician will address during your regular fall HVAC inspection. However, a sudden banging sound in the middle of winter when it’s already been running for a while might be cause for concern.

Why this happens: One explanation for the loud, sudden boom in the middle of winter is expanding and contracting ductwork. If you have a central HVAC system, you’re probably used to hearing your ducts expand and contract from time to time during the heating season.

Unfortunately, noisy ducts aren’t the only potential cause of this sound. A loud, sudden boom could indicate a gas buildup in your system, which can ultimately lead to dangerous and expensive damage, like a cracked heat exchanger.

What you can do: If you’re confident it’s the ducts making that noise, seal and insulate them or replace your air filters.

If you’re unsure why your furnace is making noise, or it’s not the ducts, turn off the system and contact an HVAC professional immediately.

Rattling

A rattling sound from your furnace can indicate a mechanical problem that may be easy to fix.

Why this happens: After years of consistent use, it’s possible that a panel or screw in your heating has come loose, resulting in a rattling sound.

What you can do: First, be sure to cut off the power to your furnace before attempting to fix the problem. Once the power is turned off from the source, you can inspect the furnace and tighten up any loose panels or screws.

If you don’t find loose panels or screws, there’s a chance your heat exchanger is faulty. A damaged heat exchanger can result in dangerous gas leaks, putting you and your family at risk of carbon monoxide poisoning. It’s essential to call an HVAC service ASAP if you’re unable to fix the rattling sound on your own.

Metallic Scraping

Screeching, metal-on-metal sounds are not only unpleasant but can also indicate a serious problem with your furnace’s blower wheel.

Why this happens: It’s possible that the blower fan has slipped out of place, causing the blades to hit the casing. This is usually an easy repair as long as the blower fan and wheel haven’t been damaged in the process. If your blower’s fan blades are seriously damaged or broken, your blower fan will likely need to be replaced.

There’s also a small chance that the part that connects the blower assembly and the motor has broken, leading the entire assembly to detach and fall out of place.

What you can do: Not much. This is the type of problem that requires an HVAC professional to come over and inspect, diagnose, and repair the issue. Make sure to call a professional as soon as possible, as running your furnace with a broken blower wheel could result in more costly damages down the road.

High-Pitched Whistling

Luckily, squeaking or whistling sounds are usually the least concerning of furnace noises.

Why this happens: There are several reasons why your furnace might make a whistling sound:

• A loose or damaged blower belt
• Dry shaft bearings
• Blower motor malfunction
• Clogged air filter
• Obstructed or damaged duct

What you can do: First, try changing your air filter or opening all your air vents to clear any clogs. If that doesn’t work, and you think the problem is caused by one of the other reasons listed above, call an HVAC technician, as you might have parts that need replacing.

Buzzing

A furnace buzzing noise is usually a low-frequency hum. If the buzzing noise resembles an electrical hum even when the furnace is off, it might be normal, but always call a pro when in doubt.

Why this happens: There are several possible causes, including a failing motor, loose air ducts, or issues with components like transformers and capacitors. If the noise persists, it could indicate a malfunctioning starting capacitor, requiring replacement to ensure the motor gets the necessary jolt to start turning. For older furnaces, a buzzing noise may suggest a failing transformer that needs replacement.

What you can do: Check for loose ductwork that vibrates when air flows through or inspect the blower motor for proper lubrication. If that’s not the cause, or you can’t find the cause, call a pro.

Clicking or Popping

This noise is often characterized by sharp, repetitive sounds resembling clicks, pops, or bangs.

Why this happens: The expansion and contraction of ducts can cause clicks as they adjust to temperature fluctuations, which is generally harmless. However, persistent or loud noises may indicate underlying issues. Clicking during ignition attempts could be linked to a malfunctioning spark igniter or problems with the pilot light/burners.

What you can do: Start by checking for loose ducts and securing them. If the problem persists, call an HVAC professional.

Call CroppMetcalfe for All Your HVAC Repair Needs

Whatever kind of weird noise your furnace makes, CroppMetcalfe’s 5-Star technicians are ready and able to diagnose the problem and fix it. Contact us 24/7 for your HVAC/heating needs all year long.

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